Thailand's government is trying to negotiate an end to protests by rubber farmers that have blocked roads and caused disruptions in the country's south.

The farmers have been hit by falling global rubber prices, and they say the Thai government isn't doing enough to help them.

Their protests have escalated in the same week that the government has extended a controversial rice subsidy program, that is seen to be favouring northern rice farmers.

Dr Viroj Naranong specialises in Agricultural economics at the Thailand Development Research Institute.

He says the farmers' expectations about the extent of government support are unrealistic because the price trend is decreasing, "they are asking the government for 100 baht per kilogram, or compensation to make the total 100 baht per kilogram."

He thinks rubber farmers are resentful that rice farmers in the north are receiving large subsidies to offset low prices.

Thailand is the world's largest rubber exporter, but the farmers who tap the trees on plantations in the country's south are bearing the brunt of a global slump.

Rubber prices have roughly halved over the past two years, with experts blaming overproduction across South-East Asia.

Farmers protesting in Surat Than say it's hard to make a living because the price of everything is increasing and a higher rubber price would make a huge difference to them.

This week President Yingluck Shinnawattra's cabinet decided to extend a hugely expensive program that has seen the government buying rice from farmers for well above market rates.

The rubber growers are in the opposition Democratic Party's stronghold, whereas the northern rice growers supported the Red Shirt movement that eventually resulted in Yingluck becoming President.

Since she introduced the rice-buying scheme in 2011, it's accumulated losses of nearly 4 and a half billion US dollars.

Despite the government introducing new caps on how much individual rice growers could claim this week, the program is expected to cost Thailand another billion dollars this year.

Dr Naranong says its understandably a divisive program, "a lot of people feel badly about this program because it's cost the government a lot of money, and it's already been badly managed and has led to a lot of corruption."